Process for mixing and wetting solid materials



Dec. 22, 1964 w. LGDIGE ETAL 3,152,428

PROCESS FOR MIXING AND WETTING SOLID MATERIALS Filed May 16, 1962 2 Sheets-Sheet 1 Fly] 3 INVENTORS M4 an! 1 00/4 59/72 100/6 z/axtr Z uc/rf gm/m Own Jaw/w Dec. 22, 1964 w. LQDIGE ETAL 3,162,428

PROCESS FOR MIXING AND WETTING 501.10 MATERIALS Filed May 16, 1962 I 2 Sheets-Sheet 2 I Minn/v Za /a! Y Fm/TZ 0 6 15 Jan; 1 u h 65034 0/955 United States. Patent ()filice 3,162,428 Patented Dec. 22, 1964 3,162,428 PRDCESS FGR MIXING AND WETTING SOLID MATERIALS Wilhelm Liidige, 9c Elsener Strasse, Fritz Ltidige, 9b Elsener Strasse, Josef Lucke, 13 im Lohfeld, and Georg Ohs, all of Paderhorn, Germany, assignors to Wilhelm Ltidige, Fritz Liidige, and Josef Lucke, all of Paderborn, Germany Filed May 16, 1962, Ser. No. 195,062 Claims priority, application Germany, July 15, 1961, L 39,550 2 Claims. (Cl. 259-9) It is known that solid materials may be mixed and/ or wetted with liquids by the so-called hurling and whirling process. In the process which is carried out in mixers having a horizontally positioned drum container, a shaft extending horizontally therethrough, arms arranged perpendicularly and helically on said shaft and mixing tools at the ends of said arms extending close to drum wall, the container vessel is filled with the materials to be mixed only to such an extent that space suflicient to carry out said hurling and whirling process is left above them, and the material is then subjected to the action of suitable mixing tools which may preferably be of oneor doublesided ploughshare form in such a manner, i.e. with such a speed that portions of the material are constantly lifted away from the material accumulated at the bottom of the container into the empty space where they are hurled and whirled around into all directions. Liquids for being admixed to or wetting, the material may be sprayed on the material at the bottom of the container and/or on the portions of material which are in a state of motion. In this known process, the container is filled to about 40 to 60% of its capacity and mixing tools are rotated in the vessel at a speed of about 2 to 12 metres per second depending on the type of material being treated and the apparatus used.

It is an object of the present invention to provide for a new and improved process for mixing and/or wetting solid materials.

It has now been found that the mixing process may be improved so that the times required for mixing may be reduced to less than half of those customarily used and the frictional forces may be reduced so that delicate structures of the material are not destroyed or changed by mechanical or thermal effects. This improvement is combined with a reduction of the power output required for the mixing tools. These results are achieved by charging the mixing container with material to be mixed to less than 30% of the capacity of the container and by adjusting the peripheral speed of the mixing tools in such a manner that the material being mixed substantially does not accumulate at the bottom, but partly forms a ring rotating on the inner wall of the drum and partly is hurled and whirled around in the empty space of the container into all directions, i.e. forms a fluidized bed or solid-air dispersion. .No particle of the material is at any time subjected to gravitation alone, but is constantly in a state of movement caused by the mixing tools. This manner of carrying out the hurling and whirling process is particularly advantageous when it is desired to carry it out continuously. Although the percentage of the volume of the container utilized is less, the increase in the rate of throughput of such a continuous process is considerable and mixing is much more accurate, because the relatively small amount of material present at any one time in the mixing drum is mixed and wetted with liquid in a surprisingly short time. The new process, however, is advantageous also when it is carried out discontinuously.

The principle underlying the invention consists in preventing the material to accumulate in considerable amounts at the bottom of the container, because the particles in such a heap of accumulated material are not so easily subjected to the mixing and Wetting process as the particles being hurled and whirled around in the empty space of the container or in the ring of material on the inside of the wall of the drum. It has been found that accumulation of material at the container bottom may be avoided if the quantity of material in the container is maintained below 30% of the effective capacity, but preferably about 20%, and if the peripheral speed of the mixing tools is adjusted to obtain the above described results. Under these conditions, an increase in the mixing accuracy and/ or in the rate of throughput is obtained.

The invention is particularly advantageous for wetting or covering solid materials with liquids. The apparatus for spraying the liquid can be fitted inside the container so that the liquid spray is distributed over a large area on the solid substance being hurled and whirled around or being in the ring. In some cases, it may be desirable to provide several spray apparatus to cover the whole internal volume of the container which is conveniently a drum. For this purpose, it is advantageous to use nozzle atomizers. It is, however, preferable to use centrifugal atomizers comprising several superimposed rotatable centrifuging disks. These centrifugal atomizers are distinguished by the fact that they can cover a large volume. The centrifugal atomizers spray the liquid out in a multiplicity of superimposed planes. In this connection again, the advantages of the process of the invention are particularly effective if the process of covering and wetting the solid materials with liquids is carried out continuously.

The combination of high mixing speeds with a low degree of charging the mixing container, and even and wide distribution of the liquid produces effects not hitherto obtainable in the covering and wetting of solids with liquids even though the size of the apparatus and the cost of operating it are much less than with prior known apparatus of similar kind, and the conditions to which the material is subjected are much less harsh. For example, the mixing in a continuous process of about 40 cubic metres per hour of a material in the form of flakes and covering the particles with a small amount of liquid, can be done in a machine having a gross volumetric capacity of 3 cubic metres when applying the process of the invention, i.e. when this machine is filled to 15 to 20% of its capacity, the quantity of material present in the mixer is 0.45 to 0.6 cubic metre; in this example the material remains in the mixer for 0.9 min ute. The current consumption for driving the mixing tools is only slightly above the consumption of the empty mixer, and the temperature of the material leaving the mixer is practically the same as that of material entering the mixer. The same result could not be achieved by the known processes in machines of the same size even with a current consumption exceeding many times that of the empty machine and causing a temperature rise of the material from about 20 C. to 45 C. In a machine three times that size, with a correspondingly high current consumption and a temperature increaseof the material of 10 to 15 C., the problem could be solved by the usual methods but with less accuracy and the time required would be about 6 to 8 times as long.

The process of the invention may be used for mixing and/or wetting dry or moist solid materials in the form of fibres, granules, powder or flakes or the like.

The process of the invention and particularly the mixing and simultaneous wetting will now be described with reference to the accompanying drawings inwhich FIGURE 1 is a longitudinal section of an apparatus suitable for mixing and Wetting the material in a con tinuous manner with a horizontal drum.

FIGURE 2 is a corresponding cross section.

FIGURESB and 4 are diagrams illustrating the process of the invention.

FIGURES 1 and 2 show a horizontal container drum 2 through which a material which is to be mixed and wetted passes continuously. It is'also-possible to use this apparatus for a non-continuous process, but is more advantageous for a continuous working manner. The material is supplied to the drum through an inlet 1 by means of a measuring device known per so. A plurality of staggered arms are arranged in manner known per se, preferably helically distributed, on a shaft 3 extend ing through the drum. Mixing tools, preferably blades 4'in the form ofoneor double-sided ploughshares, are arranged at the ends of these arms. The shaft 3 is driven by the motor 5 through a belt drive. The'material entering through the inlet 1 is rotated by the mixing tools 4 -'so that the centrifugal force acting on the material'con- 'verts it into a rotating ring on the inside of the wall of the drum 2. Liquid is sprayed into the m'ovingmaterial by spray elements 9, preferably centrifugal ato'mizers.

mixed by altering the material in such as to form a closed rotating ring 6 of "material which is not to any appreciable extent compressed although practically no particles drop out from said ring as a result of gravity. The speed of rotation also depends on the form of mixing tools; that is to say, the

better their form is adjusted to the material froma flow technical point of View, the greater will be the relative speed between the mixing tool and the ring of material.

The thickness of the ring 6 of materials is practically uniform. It is slightly thicker at the bottom of the container2 and is slightly reduced at the top. As the mixing tools 4 are faster than the rotating ring 6, the tools 4 continuously lift particles of material from the ring. These particles slide along the curved surface of the blades and are thereby accelerated and are whirled at increased "speed into the space 8. They are reflected against adjacent tools and hit against one another and constantly change their path, so that there'is in the empty 1 'space of I the drum container a dispersion of particles in air'in a state of vigorous movement. As the machine isfilled to only about 10 to 30%, preferably about 20%,

the ring of material is notv thick, so that the space available for whirling particles is large.

t The ratio of the amount of material in the ring to the amount of material dispersed in air dependson the prop erties of the materiaL'the constructionof the apparatus and the speed at which the material rotates. If the op- I erating "conditions are constant, the ratio is also constant; The particles in dispersion may reunite with the ring; they may be brough back to the ring by suction at the rear surfaces of thetool and by gravity. Thus, there is a continuous exchange of material between the ring 4 and the dispersion. To illustrate the velocities and move ments, the length of the arrow 13 corresponds to the speed of the mixing tools 4, 14 corresponds to the smaller velocity of the ring of material and the arrows 15 in dotted lines illustrate how the particles of material are deflected at higher s'peedfrom the'blades into the space. The liquid is sprayed into the space in a very finely divided form by means of the centrifugal atomizer 9 inside the ring 6. The direction in which droplets 16 from the elements 9 travel is also indicated. Owing to the fact that the planes of rotation of the particles of solid are at right angles to that of the liquid droplets 16,-the velocity of the two relative to eachother is very high and turbulence is produced inside the container by the air currents produced by the two components. The liquid sprayed out by the atomizer 9 encounters the rapidly rotating ring'6 on its inner upper surface and the particles dispersed in the space. With the aid of these intensive processes it is possible 'to cover the solid particles very uniformly and Wet them very'uniformly in a very short time. I

FIGURE 4 illustrates the same mixing process, except that in this case, the materialiswetted and covered with liquid by means of a nozzle system 12 which is so ar- [a shaft extending horizontally therethrough, supporting arms on said shaft, and mixing tools at the end of said supporting arms and close to the drum wall, with a quantity of solid material not exceeding 30% of the gross volunite of said drum container, rotating said mixing tools at such a peripheral speed that the material substantially collects in a rotating ring 'of'material on the inner wall 'of said drum container and partly is hurled and whirled around in the' empty spacewithin said ring of material, and spraying a liquid onto the inner surface of said rotating ring'of material and'on the particles of solid material hurledand whirled around by means of a spray device arranged in the space of the drum container surrounded bythe rotatingring ofma'terial.

V 2. :A process as claimed in claim 1, wherein the container is charged with a quantity of material which is about 20% of the gross volume of the container.

References Cited by the Examiner UNITED STATES PATENTS 1,218,354 7 3/17 Baldwin.

2,161,508 6/39 Ensor 259-9 2,679,385 5/54 Lodige 259-9 FOREIGN PATENTS 1,007,498 5/57 Germany.

1,082,576 6/60 Germany.

WALTER'A. SCHEEL, Primary Examiner.

IRVING BUNEVICH, Examiner. 

1. A PROCESS FOR MIXING AND WETTING FIBROUS, GRANULAR, POWDEROUS OR FIAKE-SHAPED SOLID MATERIALS COMPRISING FILLING THE MATERIAL TO BE MIXED AND WETTED INTO A MIXING DEVICE HAVING A HORIZONTALLY POSITIONED DRUM CONTAINER, A SHAFT EXTENDING HORIZONTALLY THERETHROUGH, SUPPORTING ARMS ON SAID SHAFT, AND MIXING TOOLS AT THE END OF SAID SUPPORTING ARMS AND CLOSE TO THE DRUM WALL, WITH A QUANTITY OF SOLID MATERIAL NOT EXCEEDING 30% OF THE GROSS VOLUME OF SAID DRUM CONTAINER, ROTATING SAID MIXING TOOLS AT SUCH A PERIPHERAL SPEED THAT THE MATERIAL SUBSTANTIALLY COLLECTS IN A ROTATING RING OF MATERIAL ON THE INNER WALL OF SAID DRUM CONTAINER AND PARTLY IS HURLED AND WHIRLED AROUND IN THE EMPTY SPACE WITHIN SAID RING OF MATERIAL, AND SPRAYING A LIQUID ONTO THE INNER SURFACE OF SAID ROTATING RING OF MATERIAL AND ON THE PARTICLES OF SOLID MATERIAL HURLED AND WHIRLED AROUND BY MEANS OF A SPRAY DEVICE ARRANGED IN THE SPACE OF THE DRUM CONTAINER SURROUNDED BY THE ROTATING RING OF MATERIAL. 